Journal of Agricultural Science; Vol. 10, No. 11; 2018 ISSN 1916-9752 E-ISSN 1916-9760 Published by Canadian Center of Science and Education The Effects of Kefir Usage for Probiotic Purpose on Growth Performance of Brook Trout (Salvelinus fontinalis) Huriye Ariman Karabulut1, Ilker Zeki Kurtoglu1 & Ozay Kose1 1 Department of Aquaculture, Faculty of Fisheries, Recep Tayyip Erdogan University, Rize, Turkey Correspondence: Huriye Ariman Karabulut, Department of Aquaculture, Faculty of Fisheries, Recep Tayyip Erdogan University, Rize, Turkey. Tel: 90-535- 619-2784. E-mail: [email protected] Received: July 5, 2018 Accepted: September 2, 2018 Online Published: October 15, 2018 doi:10.5539/jas.v10n11p101 URL: https://doi.org/10.5539/jas.v10n11p101 Abstract The effects of probiotically used kefir on growth, survival rate and meat yield characteristics of brook trout (Salvelinus fontinalis) were investigated in this study. For this purpose, kefir was added to trial diets at different rates 20 ml/kg feed (G2), 40 ml/kg feed (G3) while commercial fish feed was used as a control 0 ml/kg feed (G1). Total 270 fish with mean weight 24.38±0.37 g were used during the experiment. Each group had three replicate, and 30 fish were placed in each tank. Experiment was carried on for 90 days. At the end of the experiment, some growth parameters, survival rate and meat yields of the groups were determined. The best weight gain (WG), specific growth rate (SGR), feed conversion ratio (FCR) and survival rate (SR) values were obtained in G2 (20 ml/kg) group (104.31±0.11, 1.30±0.08, 1.40±0.18, 98.88±0.51 respectively). At the end of the study, the differences between the control group and the other groups were not statistically significant in terms of FCR, Condition factor (CF) and survival rate (P < 0.05). However, the differences between the control group and the other groups were statistically significant in terms of WG, WGR and Wf (P < 0.05). The statistical difference between the G2 group and the G1 group was not significant at the SGR, whereas the statistical difference between the G2 group and the G3 group was significant (P < 0.05). The body composition of the fish, hepatosomatic index (HSI), viscerosomatic index (VSI) values, fish meat crude protein and crude fat content were not affected by the addition of kefir to fish diet at different ratios. As a result, it was observed that the addition of kefir at 20% of the diet positively affected the growth performance and survival rate of the brook trout. Keywords: Salvelinus fontinalis, kefir, growth, survival rate 1. Introduction As in aquaculture, the goal of all sectors of farming is yield. The idea behind using feed additives to increase yield is to affect the metabolism of the animal and increase its rate of utilizing the feed. This way, it is possible to achieve healthy development and higher yield with less feed (Karabulut, 2008). Several studies used probiotics to increase growth performance and strengthen immune systems of farmed fish (Korkut et al., 2003). Probiotics are microorganisms that are known to be beneficial to living beings which compete with pathogenic bacteria in cultivation conditions and are not pathogenic or toxic (Yaman, 2000; Ozdemir & Kelestemur, 2009). According to the Turkish Food Codex Communique on Fermented Milk Products, kefir is a milk product that is a dairy product that fermentes lactose in fermentation (Kluyveromces morxianus) and has yeast cells (Saccharomyces unisporus, Saccharomyces cerevisiae and Saccharomycess exiguus) that do not ferment lactose. However, in the fermentation process, Kefir grains are used which have different strains of Lactobacillus kefir, Leuconostoc, Lactococcus and Acetobacter genus in particular (Anonymous, 2009). Kefir, active kefir grains added to milk, is a dairy product formed as a result of lactic acid and ethyl alcohol fermentations (Guzel Seydim et al., 2000). Kefir, which is similar in contents to yogurt, contains various beneficial bacteria and yeasts, especially species of Lactobacillus (Rea et al., 1996; Jianzhong et al., 2009). Kefir grains are yellowish white in color, irregularly shaped, similar to cauliflower, 3-20 mm in diameter. When kefir grains are added into the milk (25 C and 22 hours) they ferment the milk and reveal the kefir product. Kefir grains can be removed by filtration through the kefir product and used again in the next process. As the process repeats over time, kefir grains grow volumetrically and multiply (Guzel-Seydim et al., 2000). 101 jas.ccsenet.org Journal of Agricultural Science Vol. 10, No. 11; 2018 Kefir grains filtered through kefir product can be kept in water for 10 days at 4 C after being washed with cold water (Yıldız, 2009). Bacteria and yeasts in kefir grains are found embedded in a matrix of polysaccharide structure called “Kefiran” (Frengova et al., 2002; Riamada & Abraham, 2006). Kefiran, an exopolysaccharide of lactobacilli species, constitutes 24% of kefir dry matter (Micheli et al., 1999). Microorganisms in kefir take position on the intestinal mucosa in the gastrointestinal track and facilitate increase and development of beneficial bacteria, while helping elimination of harmful yeasts and bacteria (Elena et al., 2007; Guzel-Seydim et al., 2011). Various studies have been conducted on the effects of probiotics for growth performance and immunity parameters of different fish species (Bogut et al., 2000; Abd El-Rhman et al., 2009; Hedayat & Bagheri, 2009; Mohapatra et al., 2012; Andani et al., 2012). However, there are a limited number of studies which focused on using kefir, which has probiotic properties, in aquaculture. The studies that were reviewed usually focused on the Coruh trout and the rainbow trout (Can et al., 2012a; Can et al., 2012b; Can et al., 2014; Ulukoy et al., 2015; Ulukoy et al., 2016; Gumus et al., 2017). In Turkey, commercial probiotic products are usually imported from abroad and this increases feed costs (Karademir et al., 2012). On the other hand, kefir is a feed additive, which is produced easily and with low costs. In the Eastern Black Sea Region of Turkey, in addition to the dominant aquaculture species of the rainbow trout, producers also farm the brook trout (S. fontinalis) to attract consumers or as a hobby (Okumus et al., 1998). While several studies were conducted in Turkey on the rainbow trout (Karabulut et al., 2011), no study was found that have investigated usage of kefir in feed for the brook trout. This study investigated the effects of adding kefir into feed of trout in different ratios on live weight gain, specific growth rate, condition factor, feed conversion ratio, survival rate and flesh yield characteristics in brook trout (S. fontinalis). 2. Material and Methods 2.1 Experiment Area and Fish Material The study was carried out at experiment unit in the Recep Tayyip Erdogan University Fisheries and Aquaculture Application and Research Center. In the study randomly selected 270 brook trout (Salvelinus fontinalis) were used, whose weights varied between 20 and 30 g (mean: 24.38±0.37 g). The fish were randomly distributed into 80 L fiberglass tanks by 3 groups with 3 replications such that there would be 30 fish per tank. The 4 L/min average water flow was provided to the tanks. According to the measurements, the water temperature value was changed between 7 C and 12 C, dissolved oxygen value was 5-6 mg/L and pH was approximately 7.5-7.8, while the study was conducted in a natural photoperiod during winter. 2.2 Feed Material, Kefir Preparation and Bacteriological Analysis The study used a feed that consisted of fish meal, fish oil, grain products and vitamin A and mineral mixture which contained 47% crude protein, 20% crude fat, 2% crude cellulose, 10% humidity, 10% ash and 3330 kcal/kg of metabolic energy. Natural kefir grains were used in kefir production. Kefir grains were added 1 liter warm milk in the jar (5% v/w) and kept in dark for 20 hours at 22 degrees celsius (Guven et al., 2003). Kefir grains were separated by sieving after the fermentation process and kept ready in the fridge in the water (4 C) for the next fermentation process. The resulting kefir product was also stored in refrigerated conditions until the experimental feed was prepared. The kefir product added feeds were prepared daily. Prepared kefir product was not used as feed additive if it was stored for more than 3 days (Guven et al., 2003). The experimental feeds were supplied with kefir product in previously determined rates (G1 (control): 40 ml distilled water/kg feed + 0 ml kefir/kg feed; G2: 20 ml distilled water + 20 ml kefir/kg feed; G3: 0 ml distilled water + 40 ml kefir/kg feed). After drying at 20 C in a fan-drying oven of the feeds, they were covered with fish oil (30 ml fish oil/kg feed). The feeds prepared every week were stored in plastic packages in a refrigerator (4 C). The feeds were given to the fish along the 90 days (3% kg/fish weight). For the bacterial analysis of kefir, 25 ml of kefir product was mixed with 225 ml of peptone water (Oxoid Ltd., Hampshire, UK). This homogenate ten-fold dilution solutions were prepared in the same solution and 0.1 ml of parallel plates were spread from these dilution tubes. Lactobacilli were analyzed using MRS (Oxoid CM361) agar and Lactic streptococci were counted using M17 agar (Oxoid CM785). The yeasts were analyzed using potato dextrose agar (Oxoid CM139) (Harrigan & McCance 1976). In this study, Lactobacillus helvetis, 102 jas.ccsenet.org Journal of Agricultural Science Vol. 10, No. 11; 2018 Leuconostoc mesenteroides, Kluyveromyces mesenteroides and Pichia fermentes were detected as lactic acid bacteria and yeasts in kefir grains.